Unfortunately no, this command only allows up to 10.

The alternative would be the Symbols in Area command. It doesn't pack symbols tightly the same way, but by experimenting with the random arrangement you may be able to get close. While that command only lets you choose a single symbol, it has the advantage that you can ask it to use all the symbols in the same symbol group as the one you picked, technically allowing for using as many symbols as you want. There is a blog article dealing with setting up a custom symbol group just for this purpose.

Not sure how you manage to grab things that are on hidden sheets. I've never been able to do that myself. But do note that if you hide a sheet, then use a drawing tool or other command that needs to operate on that sheet, it will become unhidden, and then entities on it can be selected.

In any case, when it comes to hiding/hiding the grid, I recommend doing it using layers instead. Make sure the grid layer (usually HEX/SQUARE GRID) is both hidden and frozen. (and never unfreeze/thaw it when showing it, it should always stay frozen, as this prevents it from being accidentally manipulated when you are working on something else.)

To show/hide the layer from the command line, use the TOGLF command. This will hide the layer if visible, and show it if not. This command accepts a wildcard filter, so you can simply type

TOGLF GRID

to toggle the visibility of the HEX/SQUARE GRID layer. (Of course, the filter means EVERY layer with the word GRID in the name will be toggled, but you usually only have one).

Code signing is the process of applying a digital signature to the installer. This lets windows know that it comes from a reputable software publisher, and thus is much less likely to be malware. This also makes it more or less impossible for bad actors to modify the PF installer (to add a virus for example) since the signature would be invalidated when they changed the installer. This helps you ensure the installer is authentic.

To create the same texture at different scales, you need to make multiple definitions for it.

Simply find the relevant fill in the fill style dialog. With the desired fill selected, hit the new button, and give it a nice name. Now you have two copies of the same fill definition, and you can change the scaling for one of them. Make as many clones as you need to set up various scales.

Symbols -> Scale symbols in map doesn't set the symbols to a specific scale, it scales them by that amount. If you use that on your symbols and scale by 1, they will simply stay whatever scale they are. Same if you set it to 0.5, you halve the scale of any symbols, so if it was already 0.5, it will end up at 0.25, while if it was 1, it will scale them to 0.5. It is a command to change the scale by a relative amount, not read out the current scale.

To check the scale of any symbol, you have to do as JimP suggest, use List on them, that will reveal the current scale of that particular symbol.