Testing for Developmental Significance

Please help with my current research analysis.

I am studying university students' frequency us, confidence, and success at various study strategies throughout their university course. It is not a longitudinal study, just a snapshot study. In other words I have surveyed first, second, third, and fourth year university students (at one time) and am wanting to analyse the following:

1 - Firstly is there a significant difference between their frequency use, their confidence, and their success of a strategy, during particular years of studying. Using SPSS I have selected first year students and carried out t-tests between frequency use and confidence, frequency use and success, and confidence and success, for each strategy. I have done that for first years, second years, third years and fourth years (individually). Is that ok to do?

2 - Secondly, are there significant developmental differences between those in the first, second, third, and fourth year (for frequency use of strategies, confidence, and success). Not too sure what analysis to carry out here (MANOVAs)???

Any help would be greatly appreciated.