if a person repents from apostasy or blasphemy, will he be forgiven byAllah and if he is in islamic state will he be still executed even after becoming a true muslim

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

With regard to his repentance and whether or not it will be accepted by Allaah The Almighty in the Hereafter, then this is a matter which only He knows. However, if he sincerely repents, Allaah The Almighty will accept his repentance, Allaah willing. Allaah The Almighty Says (what means): {Say, “O My servants who have transgressed against themselves [by sinning] do not despair of the mercy of Allaah. Indeed, Allaah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.”} [Quran 39:53]

As regards killing him after he had repented, then the jurists of the Shaafi’i school of jurisprudence stated that he should not be killed. Nihaayatul Muhtaaj, one of the Shaafi’i Fiqh books, reads,

“If he becomes a Muslim, his Islam is valid and he is exempted from the punishment as Allaah Says (what means): {Say to those who have disbelieved [that] if they cease, what has previously occurred will be forgiven for them. But if they return [to hostility] — then the precedent of the former [rebellious] peoples has already taken place.} [Quran 8:38] And as per the Hadeeth which reads: “If they had said it, their blood and money become secure from me.”, and his statement means that whoever insults him, [i.e. the Prophet ] or any other Prophet and then repents, then his Islam is valid and he is exempted from the punishment , and this is according to the correct opinion.''

Allaah Knows best.