But you said "force in the blk.dat file", IDK if that's possible but if it is, I think your node wont sync past that particular block.
You'll have to delete the related data then reindex to sync properly.
[2] How to validate new transactions ?
[3] what is shown in local wallet with fake address ?
1. It will be done automatically by your node.
2. It will be done automatically by your node.
3. There's no such thing as "fake address" and faking blocks won't affect your wallet.dat.
Based from this questions, you should start with the basics than trying to solve these scenarios.
I'll recommend you to read Mastering Bitcoin, pdf download link in the "see also".
It has everything you need to know.