Whilst the paragraph descriptions are well written my suggestion on your current role for example would be to keep the first paragraph in place and immediately after that I would bullet point a list of your primary responsibilities.
Overall it is a decent CV but I'll have a proper look and send you the feedback directly over the next day or two.
Chronologically (earlier first) it went like this:
Company 1 (1 year)
University (1 year)
Company 2 (3 months)
Company 1 again (nearly 1 year)
Does it raise questions that I left Company 2 after only 3 months, and that I went back to Company 1?
(not listing company names here so it doesn't get into their search results)
It does and you will be questioned on this.
The fact is, if you have a reasonable, logical, verifiable reason for returning then it won't be an issue.
If the company 2 role was a contract position I would highlight that on the CV.
No, I've never done contract work. I won't go into details here, but I feel I have good reasons for leaving C2. They were great to work for, but just weren't quite in line with my career goals.