Moving from 3.8 to 4.2

[BillB1]

Gentlmen,

I need your advice on how to upgrade to 4.2.5
Testing on local PC using XAMPP:

Old Forum:
PHP Version: 5.6.32
Myadmin: 4.7.4
Vbulletin: 3.8.11
Custom syles
Runs perfect!

New forum:
Migrating database to
PHP 7.1.1
Myadmin: 4.6.5
Vbulletin: 4.2.5

Questions:
1. Do I create a new database and install VB 4.2.5 first then import vb 3.8 backup to it?
2. or Create new data base, restore vb 3.8 back up ?
3. In all cases when installing vb 4.2.5 it over writes the entire database tables.
4. I wish to keep the vb3.8. customized style, is there a tool to modify/upgrade the style to vb4.2?

Note:
If all goes well, I'll be upgrading to VB5

Thanks
Bill