Arduino for STM32

There is no such thing as PWM mode for pins.
You can set pin in INPUT or OUTPUT (with pull-up or pull-down also) mode.
For analogWrite you don't need to set pin mode, as analogWrite does it.

How do you check if PWM works ??

... By any chance, if you want to do Serial1 through 'PB6 and PB7', How should I set it as source code? can you give me an example? (You must be busy, sorry for asking.) With STM32 core it's easy: Serial1.setTX(pin); Serial1.setRx(pin); You'll find it on STM32duino wiki: https://github.com/stm32dui...

On STM32 interfaces have alternate pins. It's done this way so you can choose which pins to use. For example by default U(S)ART1 uses PA9 and PA10, but you change it to PB6 and PB7. Same thing with SPI. By default SPI1 uses PA4-PA7, but if you need those pins as analog inputs, you can set SPI1 to us...

STM32 MCUs do not have EEPROM. To have non-volatile memory, virtual EEPROM is created in flash memory. Because every MCU has different memory it virtual EEPROM needs to be configured for each MCU. You're using Roger's/Steave's core, so it's limited to only few MCUs and it may be missing necessary c...

It's an USB bootloader, but it does not use COM port for firmware upload. COM port is used only to reset board and you need to flash firmware with USB Serial enabled to see COM port.

Also, it's an old bootloader, HID bootloader is a better option: https://github.com/Serasidis/STM32_HID_Bootloader/

You need to enable USB CDC in your sketch, otherwise COM port won't be enabled.
If you don't enable USB CDC you can enter bootloader by setting boot1 jumper to 1 position and resetting board (if you flashed HID bootloader).

5V pin, USB 5V, ST-Link 5V all are connected to one point. If it runs powered from USB, it has to run powered from 5V pin. BUT your 5V supply needs to be 5V +/- 0,25, not 4.5, nor 5.5V If you did what manual says, LD2 cannot lit up when powered with 3.3V pin. SB14 needs to be OFF (removed / not brid...

Have you read this:
https://www.st.com/resource/en/user_man ... ronics.pdf

There is no such thing. STMs do not need to reset on USB connect like AVR Arduino boards.
If your board resets then it's rather hardware related.

STM32 examples for timers are for STM32 core, not for a specific MCU. You don't have to adapt anything.