Cheat Engine

[desertricker]

I have 3 questions about this;
1-)lets say I want to change a value,but not itself,I want to change the instructions that calculates it.An example;when I look the instruction that writes to the health I see there's a opcode like this

"mov [esi],eax"

I check the value of eax and it tells me the last value of health,but I want to find an opcode like

"sub [esi],01"

so I can change it like

"add [esi],01"

2-)It's easy to follow a code like this

"movq [ecx+02],xmm0"

If the adress of value that i want to change is [ecx+02] I should change the xmm0 register so I look what opcodes writes to xmm0,but here comes my problem if the opcode is like this;

"mov eax,[esi]"

should I look which opcodes writes to [esi](like mov [esi],eax) or should i take the address of [esi] and search about it?

3-)I sometimes see opcodes like [esi+04] and [esi+14] in same function I look their addresses it's like for the first one it says esi=0000A3B4 for the second one it says esi=0000A3A4 when we calculate them for the first one 0000A3B4+4=0000A3B8 for the second one 0000A3A4+14=0000A3B8 so they both point the same adresses but they are different in opcodes how can [esi+04] and [esi+14] in same function can point the same address?

btw some of these question may be sound stupid to you since I'm a beginner yet