Confirmation for Tx that is out of main chain

[BitCoinDream]

For a certain Tx, where main_chain = false after receiving a few confirmations, can it still receive confirmation ?

[Jan]

For a certain Tx, where main_chain = false after receiving a few confirmations, can it still receive confirmation ?

So what you say is that it was confirmed, but on an orphaned chain.
Yes. If the transaction is still valid (the inputs were not spent in another tx on the main chain, etc), then a miner can choose to include it in a block, and it gets confirmed (again). This happens quite frequently when two competing blocks are mined about the same time.