What iron to take with a reserve for the future in the minimum budget?

Question

Iron

Good day!
Recently, I became a junior developer (which I wanted for a long time, by the way). I work in Unity3D, but for 2D games for smartphones, and the tasks I have so far are simple)
At home I sometimes (only 6 hours a week) work in Unity on my old laptop (both for work and on my own games ), for which you can work, but it's still a pleasure.
I decided to assemble a computer for little money with the possibility of further "finishing" it.
Accordingly, the tasks are:
1. Fairly simple projects in Unity, Visual C # (moreover, the Express version is enough for my eyes so far)
2. At night, downloading high-definition movies (either a second HDMI for TV, or over the network on TV)
3. A year later, a new Doom comes out) Yes, its system requirements are not known, but I flirted with old thoughts as a student. Otherwise, I don’t pay attention to games - there is an old game console, and I play games so “often” that for so many years I haven’t tried all the games from its TOP20 (although they gather dust on the shelf).
4. Compact and no noise. Since there is no video card yet (except for the built-in one), the computer will probably work around the clock. And compactness - I just like mini-itx and other compact systems, but if it noticeably affects the budget - I'll get by, there will be enough space for the system unit.
What I looked at:
1. FullHD monitor with HDMI inches so 22 - 7000 rubles.
2. Processor Intel Pentium G3220 OEM - 3590 rubles.
3. RAM 4 Gbx1, 1600 MHz, PC12800, 11-11-11 - 2290 rubles.
4. SSD drive A-Data SP900 - 2950 rubles.
Actually, the questions are:
1. Of course, I want a core i3 4130, but is it worth paying 7000 for it in my situation, or is it easier to "throw away" the Pentium in a year and a half and install a Core i3 or i5 that was modern at that time?
2. Then add up to 8 GB of memory - for my tasks in Unity 8 GB on a working computer is enough, but what about games?
3. Math. payment for this case? Here in the chipsets I'm behind, I don't follow
4. For those who play modern games - advice in general, from experience - which video cards will become cheaper after NG, but will they give out a decent level of performance? (the maximum graphics level is not needed, but under the resolution of the monitor, clarity of vision will not interfere, and it is possible that I will play on a 40-inch TV)

Answer 1

read Can you explain on what parameters to choose PC components?