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Hibernate 5.4 filter support with JPA 2.1

Have search on many place's but did't found a single statement about the Hibernate filter (5.4) version support with JPA 2.1
Is JPA 2.1 and hibernate filter 5.4 compatible or not ? I can see most of the things are depricated by Hibernate in 5.4 So not sure if we can still used filter with JPA 2.1 (with EntityManager) or not.
Also, How can we used that ? Can anyone please share any example for reference ?
Note: I saw we can used unwrap<> things to work with Entitymanager as session I think depricated in Hibernate 5.4.
Thanks!!

Migration from Hibernate 3.2 to 4.3.9 TransactionHelper class not found

I am new to Hibernate but have been tasked to migrate from 3.2 to 4.3.9 I am having problems with class/methods not found. Typically getSession, TransactionHelper, SessionFactoryImplementor, PropertiesHelper.
If these are no longer available in version 4.2 what do I replace the above with?

Based on your tags you are using Spring Framework. If you have this option, instead of using plain Hibernate switch to JPA (the difference is explained in this question) with some friendly libraries e.g. Spring Data JPA. This should abstract your code from the semantics of Hibernate version (although this is not that simple).
Please note that Hibernate 5.3 was released on 24th Jul 2018. By updating to 4.2 you are updating to a legacy version.

why we need to define dilect,when we have already defined driver in configuration file in hibernate

In many of document I found we have to define dialect in hibernate.cfg.xml to tell hibernate what language we are going to use in or hibernate.On the basis of this hibernate generates respective sql.
<property name="hibernate.conection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.dilect">org.hibernate.dialect.MySQLDilect</property>
More over this could be possible multiple driver for any database provider and also for any driver there could be multiple dialect as per their version.
My point is even when we have already mentioned driver(unique) there and at a time we are single version of jar,then why this is not only sufficient to generate sql.

The dialect is an optional configuration option. Usually hibernate can autodetect a dialect based on the database connection.
But there are some cases you might want a different dialect
- Different versions of database might require different Dialects.
- Customize/Bugfix a dialect and specifying it.

Are you are assuming that the Driver is unique and can be used to fin which database to connect? Well, you can have many driver classes that support the same database. May be for MySQL now there is one common driver, but consider Oracle.
There are many drivers for Oracle. Check this http://www.oracle.com/technetwork/java/index-136695.html
If Hibernate has to use any one of the possible drivers that you specify, how will it know what dialect (SQL syntax) to use? So you need to specify both the Driver class and the Dialect to Hibernate.

Connection drive class merely point out Database Management System (DBMS) vendor. Because one DBMS, vendor has many versions, per version has a specific set of functions. By the time, per DBMS add more features. For example:
Oracle
Oracle 8i (released in 1999) use org.hibernate.dialect.Oracle8iDialect
Oracle 9i (released in 2001) use org.hibernate.dialect.Oracle9iDialect
Oracle 10g (released in 2003) use org.hibernate.dialect.Oracle10gDialect
Oracle 11g (released in 2007) use org.hibernate.dialect.Oracle10gDialect
Oracle 12c (released in 2013) use org.hibernate.dialect.Oracle12cDialect
This is full list of dialect at current version:
https://docs.jboss.org/hibernate/orm/current/javadocs/org/hibernate/dialect/package-summary.html

Does Hibernate 5 still support Hibernate Spatial?

According to the following link:
http://docs.jboss.org/hibernate/orm/5.1/quickstart/html_single/#_release_bundle_downloads
There should be a folder "lib/spatial" that contains the hibernate spatial jars, however it seems to be the one folder missing in the lib folder from the standard download. (I've tried Hibernate versions 5.0.6, 5.0.8 & 5.1.0).

Yes, the move has been completed, and hibernate-spatial is now part of Hibernate 5.x.
You can always get access to the jars using http://search.maven.org/ (just search for hibernate-spatial).
I'll ask on the hibernate mailing list why it isn't included in the lib folder as documented.

Hibernate 5 is not supported yet. If you check the official website:
hibernatespatial
You will see:
Compatibility with Hibernate ORM
Hibernate Spatial version 4.3 is compatible with Hibernate 4.3.x only
Hibernate Spatial version 4.0 is compatible with Hibernate 4.x only
Hibernate Spatial version 1.1.x is compatible with Hibernate 3.6.x
Hibernate Spatial version 1.0 is compatible with Hibernate 3.2.x - 3.5.x
But do not be afraid, the work has already started on Version 5. There is already a hibernate spatial jar uploaded here, but it is less than a month old.

Updating from Hibernate 3.6 to Hibernate 4.0

I want to know the key differences I need to take care of if I want to switch to Hibernate 4.0 from Hibernate 3.6 ? Does Hibernate 4.0 support hbm.xml or do I need to use JPA for mapping?

Hibernate 4 still supports ORM mapping via XML (hbm.xml). As suggested by the mapping section in this basic hibernate 4 tutorial.

You should read the migration guide
https://community.jboss.org/wiki/HibernateCoreMigrationGuide40