1. If I were to be young again, I would marry her.

2. If I were to be young again, I will marry her.

(Is #2 grammatical?)

3. If he should go there, he would be welcomed.

4. If he should go there, he will be welcomed.

(Are these two sentences grammatical? What is the difference between #3 and #4 in meaning because of 'will' and 'would'?

2 s wrong. The others are right.