If you can't tell the difference, put some tape or string around the new canes every year to keep track of which is which.

I think everyone knows this about black berries but not so much with raspberries: If you pinch the top off of a cane (I did when it hit 18") and the plant replaced the top with 4 or 5 new tops. I only did this around the perimeter and this is the first time. So I don't know what that means in total berry production. The rest of the bush is too dense to benefit from top pinching. That is probably why it is not generally done. With raspberries you can get away with experimenting and mistakes.

That depends. If they are June bearing raspberries yes.
If everbearing you can cut the top one third and have a 2nd crop, the 2nd year. Or cut them down after first crop. Your choice to take a 2nd crop, or not.
Some argue it is better to take one crop. I myself disagree.

Some everbearing cultivars really produce a large 2nd crop, like Fall Gold. It's worth taking a 2nd crop. I think others do not produce well, but it also depends on area.
Colder regions have good 2nd crops. I average 50 berries per cane for a 2nd crop on established plants. Sometimes more. But if you are getting a small 2nd crop, it may be better just to cut down. Always cut right to the ground, as close as possible, leave no stalk!!

So first you have to know if you have June or everbearing raspberries.

First year cains are called primocanes. 2nd year canes are called florocanes sometimes spelled floricanes.
Usually florocanes are brown and look old. Primocanes are green! So never cut down green canes, unless thinning canes. Sometimes a plant produces many primocanes that are too close, 6 inches in general is OK, but on new plants, let them get established before thinning. Thin the 2nd year.

June bearing raspberries do not fruit on primocanes, they must age a year, and they fruit on florocanes.
Everbearing fruit on both. The top 1/3 on primocanes, and the bottom 2/3 on florocanes, the next year. If you do two crops, make sure you cut off the part that fruited. The top 1/3, they will fruit much much better the next year if you do.

It is confusing because both June and everbearing can have both primocanes and florocanes. They often are crowded together, Making cuts can be difficult. Another reason why some just cut everbearing to the ground after 1st crop. It makes it a lot easier to manage. I myself want more berries and I have to deal with both with my June bearing plants (I have both), so no getting away from it for me even if I did cut them down.

The center of the bush gets really crowded and tipping will increase that and reduce sunlight to nearly all. the ones you tipped cannot grow as fast because they are pushing more heads, so will get shaded by the untipped. Thinning inside the bush has no real advantage vs the work. If you want to tip a few do it only on the south or west edge.

You will have to dig out some shoots when the bush gets too wide for you to reach the middle when picking.

I give away what I dig out. I let them get 8" then cut them off at 3". when they grow back a couple inches I dig them and give away. I give 4-8 canes per pot. those will berry a little the same year, but do great on year 2.