Porting 4.4.2 to 4.7.0

[wysota]

I have installed the latest version of Qt (4.7.0 LGPL and Commercial).

Based on MinGW or Visual Studio?

However, after importing the code, the code fails to compile with multiple compilation issues.

After "importing" it where?

Could anyone advise why this may be happening, or point me to any QT resources that may help with porting older QT code to the latest version?

You shouldn't need to port anything. 4.7 is compatible with 4.4 on the source code level.

If an older system is written with a commercial release, does that prohibit porting the system to a later LGPL version?

You can switch between LGPL/commercial freely (both ways). This wasn't the case when Qt was GPL, then Trolls were getting angry if someone was switching from GPL to commercial.