I need some forum upgrade advice

[محروم.كوم]

Right now I'm running vBulletin 3.6.12 on my shared host, but when I first installed vBulletin 3.6.12 I was not aware that if my server host upgrades PHP version used to PHP 5.3 from 5.2.12 (that they use now). That it will stop my forum from working because vBulletin 3.6.12 doesn't work correctly with PHP 5.3.

So I have a few questions here. What would happen if from my cPanel I choose the option to use PHP 4 instead of PHP 5 with vBulletin 3.6.12. Would this stop my forum from breaking by using PHP 4.4.9 instead of PHP 5.2.12 when they upgrade later to PHP 5.3. If it would not stop my forum from breaking because I choose to use PHP 4 instead before they updated PHP 5.2 to 5.3, what Pro's and Con's do I face switching from using PHP 5.2.12 to PHP 4.4.9.

Now I have another question, if I decided to upgrade my forum from vBulletin 3.6.12 to either 3.7.7 or 3.8.5. Can I just do a straight upgrade from either version no problem? Also, does vBulletin 3.7.7 have support for PHP 5.3 like vBulletin 3.8.5 does? __DEFINE_LIKE_SHARE__