iMac had dual boot - MacOS and Windows 10. Now its only booting into Windows.

Hi Techies,

I have an iMac 13,2 (Late 2012) with following specs:

1. Processor: Intel(R) Core(TM) i5-3470 CPU @ 3.20GHz
2. BIOS Version/Date: Apple Inc. 292.0.0.0.0, 10-June-2020
3. Installed Physical Memory (RAM): 32.0 GB
4. Screen Size: 27 Inches
5. Hard Drive: 1 TB HDD
6. Installed OS: Machintosh, Windows 10 Pro

I had upgraded the HDD with a 4 TB SSD, which was mirrored from the previous HDD. After than was able to use the PC as normal, but was never able to boot into MAC. iMac would normally boot into Windows only. However, I want to use both the Operating Systems.

I tried various options to try entering recovery mode/boot from USB/entering the BIOS. But system would just boot into Windows. Tried pressing these combinations as well OPTIONs, Command + Options, Command + Option +R, Shift + Command + Option + R and various other options). But machine is just ignoring all these commands and booting into Windows.

So wondering if someone could suggest me a way to have both the Operating Systems working on my iMac now.

Regards