Combining data from two time periods from questionnaire data


I have collected data from a questionnaire for 35 participants.

At baseline: All 35 participants filled the questionnaire
At the 1st follow up (1-month from baseline): 17 participants filled the questionnaire
At the 2nd follow up (3-months from baseline): 13 participants filled the questionnaire (Of which 11 have not filled the questionnaire at the first follow up and 2 have filled the 1st follow up)

So in summary, at the follow up I received data from a total of 28 out of 35 participants. 15 only filled the 1st follow up (17-2), 2 filled both the first and 2nd follow up, and 11 filled the 2nd follow up (13-2). So the data I have at the 1-month is not from the same participants at the 3-month.

I carried out an independent samples t-test to assess if the mean values are comparable and the result I got was:

An independent-samples t-test was run to determine if there were differences in total mean scores of the questionnaire between the 1-month and 3-month follow-ups. 1-month follow-up mean score was higher than 3-month follow-up mean interval scores with a mean difference of 2.43 (95% CI, -0.15 to 5.0).
There was no statistically significant difference in mean interval scores between 1-month and 3-month follow-up interval scores, p=0.64.

My queries are:

1. Given the CI crosses 0 and the p-value is >0.05 is the result statistically significant?
2. In this case when analysing the baseline and follow up, can I combine the 1-month and 3-month follow ups? or do I analyse them separately?
3. Regarding the loss to follow up, how would I go about carrying out an intention to treat analysis?

Your help is appreciated
Hope the post has sufficient information
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