If you’re interested in KSP 1.12.5 legitimately, it’s best to get it via Steam or GOG (often on sale for ~$10-15). If you saw an article claiming to offer a free .rar of that version, treat it as suspicious.
“Yeah,” she lied. “Good flight.” kerbalspaceprogramv1125rar
Building a complex assembly, like a full sensor array or a multi-stage rocket, can take roughly of manual work . Larger models are often easier to assemble than tiny, fiddly parts, but they require more paper and ink . If you'd like, I can help you: If you’re interested in KSP 1