Is there any other way to install firmware than recovery mode or flash tool? I'm trying to re-install my phone stock firmware. (I'm experiencing bugs, I already factory reset 5 times but the bugs are still there)

Phone's chipset is spreadtrum (sc8830)

I already loaded the packet file succesfully as seen in this screenshot.

The problem is.... I can't put my phone into download mode (bug), now the tool can't detect it.

I as well already tried all of this option but still nothing.

Another bug is I can't put it into recovery mode. I tried using apps like link2sd to put it into recovery mode but it only goes to blank screen (tried that many times)

Is there any other way to install firmware than what I stated above?
Spreadtrum devices don't have recoveries, nor don't they have a ''download mode". Their bootloader is accessed with a "boot key" (usually hardware buttons) through SCI USB2Serial port.

To get the phone detected, just simply switch it off. Hold volume down button (or volume up) and plug the device to the computer. Windows should install drivers (Download and install SCI drivers). 

Open the flash tool (ResearchDownload), load the PAC file, click on run. Power off the device, hold volume up/ down, connect USB cable. Et voilà.