1. "They would do," meaning that they would be suitable, would function, would be OK for the intended use. They maybe weren't hte most attractive or in the best condition, but she hoped they would do the job and allow her to skate.
2. Having shoes/boots that are too tight is not comfortable. They are a little too small for her feet, which is why she had trouble buckling them.
3. They were too small, so she had to pull the strap real hard to get it into position to mate with the buckle. Then there was apparently some trick to getting the two to mate,which Eva understood how to do.
4. I am not sure why the word "sticky" is used here. I think she is describing the function of the interlocking mechanism of the buckle.
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