How many salutations are there in the first half of the Tarawih prayer, and is my prayer valid if I only perform two salutations?

The Prophet, peace and blessings be upon him, did not exceed eleven rak'ahs in Ramadan (definition) or otherwise. He would pray four, then four, then three, and it was a long, beautiful prayer. The night prayer consists of two rak'ahs by two rak'ahs, and if the worshiper fears the dawn, he performs witr with one rak'ah. It is permissible to exceed this number, and the Companions did so. The night prayer is not restricted by a specific number. It is permissible to pray four rak'ahs with one taslim (definition), but the Maliki school of thought is to perform taslim after every two rak'ahs.