Don't expect anything resembling what should be inside them according to the model. Not only they can be crappy parts but parts with completely wrong specs like operating frequency or voltage.
One can reasonably expect that the parts with the same markings are similar. More than that is unknown. I do not recommend the assortments for project construction stock. But for a novice with limited funds, there is a lot of educational value in figuring out how to properly characterize and apply them. For a long time I was hung up on "I need a 2Nxxxx" when in fact I just needed a transistor.
Growing up, I was dissuaded from doing many things by advice from my father. I'm sure he meant to be helpful, but he so complicated things that many projects were abandoned because it was beyond my abilities. Graduate school taught me the value of failure.
A poor instrument is better than no instrument. A stock of dubious parts is better than none. When I was a kid, it was common to buy bags of unmarked transistors. I still have some of those. I never used them because I never found out how to test them and had nothing but a VOM. Now I would breadboard an amplifier circuit and feed a pulse to them and look at the response if I had limited funds. As I now have a curve tracer, I can do far better.
One of my goals in buying some assortments is to address the problems they pose to novices. Whether wise or not, people do buy these. It seems to me measurements are more useful than innuendo.
For small signal work, the 2222, 3904 and 3906 will cover almost everything except JFETS. That used to be the MPF102, of which I still have close to 100. I'm not sure what a suitable equivalent is today. I spent a good bit of time researching the subject without finding an answer. I *highly* disapprove of publishing designs based on obsolete parts unless the relevant design parameters re explicitly stated.
Old parts that have been in production for a long time are generally good choices. However, in manufacturing saving a few cents per hundred matters. For a hobbyist it is not an issue. The 3rd ed of "The Art of Electronics" is a good reference for parts choices as well as being an education in itself.
If you think you burned a transistor, put it in a "suspect parts" bin until you learn how to test them.