Learn Dutch: Hij geeft toe aan de verleiding. - He gives in to the temptation.

Yes, toegeven has two common meanings. While it often means 'to admit' or 'to confess' (like hij geeft zijn fout toe - he admits his mistake), when you use it with the preposition aan, it means 'to give in to' or 'to yield to'. So toegeven aan de verleiding is 'to give in to the temptation'.

How could I use this lesson's structure to say 'He gives in to the temptation, only to regret it later'?

You can use om vervolgens (only to / to subsequently) plus te and the infinitive. For example: Hij geeft toe aan de verleiding, om er vervolgens spijt van te hebben. This highlights the narrative contrast between his action and the resulting regret.

If I put this in a subordinate clause, does toegeven stay split up?

No. Because toegeven is a separable verb, the prefix toe and the verb geeft stick back together at the end of a subordinate clause. For example: Ik weet dat hij aan de verleiding toegeeft. (I know that he gives in to the temptation.)

Could I use opgeven here to mean 'giving in'?