I have to ... cast my sigil for option 1. A Tremere gains his sigil when defeating his parens (no matter whether the parents holds his own sigil), or when the parens dies. Remember that there were changes between editions, and material from previous editions is no longer "canonical".
Let me add that, in general, it's not quite so hard for a filius to defeat a parens within a few decades from his gauntlet if he really focuses on it. First of all, it takes only one victory to win the sigil (remember that the filius can challenge once, plus once/decade), so even just one chance out of four of winning any given duel is good odds. Second, and perhaps more importantly, certamen "builds" can be a little like a rock/paper/scissors game: if you grow your Arts with the specific intent of beating a specific magus, you can have better than even odds with less than half his experience.
Look at this example, considering the canonical "twines" Tremere (two strong techniques, two strong forms). Consider a Tremere master with a score of:
20 in his twines (say, In/Mu/Co/An) corresponding to 840xp,
5 in every other art (165xp) for an art total of 1005xp,
6 in every relevant ability (finesse, penetration etc.) at 105xp/ability
Now consider a Tremere student with a score of:
13 in his twines (364xp total),
5 in 7 other forms (105xp) for an art xp total of 469, less than half the master's, and
4 in every relevant ability, i.e. 50xp/ability, again less than half the master's.
The student seems strictly weaker, right? Well, not if his strong forms are the same as the master's (Co and An) and his strong techniques are weak techniques for the master (say, Cr and Re). Then, the student can challenge with one of his strong techniques, and if vetoed force the other. This means that, technique-wise, the student will have 13, and the master 5. The master then chooses the form. He can either choose a strong form, that will be strong for the student too (20-13), or a weak form, that will be weak for the student too (5-5, the student vetoes his 0 form). Remembering the Tremere focus that doubles the weaker art (I'll assume either one if they are equal),
a) in the first case, the student brings to the table a 26,13 art pair, the master a 20,10 pair.
b) in the second case, the student brings to the table a 13,10 pair, vs. the master's 10-5.
The second case is probably the best for the master, but the student still has 8 points of art advantage that more than make up for his 2-point deficit in the relevant abilties, giving him more than a 50% chance of winning the duel.
I have not considered fighting styles etc. here, but even with those the student's advantage remains.
It's even better if the student does not stick to "twines" and takes e.g. just one strong form matching the master, vetoing the other; but being Tremere is all about tradition, so...