Alphabet Series double sequence

The sum of the series formed by the sequence 3,sqrt(3),1...... upto infinity is :

What will come in place of the question mark(?) in the following alphabet series based on their positions in the English alphabet? DGH JMN ?VYZ

If each vowel of the word 'GRAYHOUND' is changed to the previous letter as in the English alphabetical series and each consonant is changed to the next letter as in the English alphabetical series then in new arrangement how many letters are repeated?

In alphabet series, some alphabets are missing which are given in that order as one of the alternatives below it. Choose the correct alternative. 2 - - 1 - 323 - - 23