No; your customisations are on top of an 12.1 module, which could well have changed. You need to
1) Ensure you have copies of both the original and customised 12.1 module.
2) Compare the original 12.1 module to the corresponding 12.2 module.
3a) If the two modules differ then you need to re-apply the customisations on top of the 12.2 module.
3b) If the two modules are identical then you can likely reapply the existing custom module into the 12.2 environment.
My comparing, I mean comparing version numbers, comparing text versions of the forms etc.
Customized environments require additional attention during an upgrade. You can follow the Oracle E-Business Suite Developer's Guide instructions. Hope it helps
can you elaborate on specific pages to look into Oracle E-Business Suite Developer's Guide instructions?