Assalamualaikum - Questions about starting Salah and Tahajjud

Assalamualaikum brothers and sisters, I'm new to Islam and plan to take my shahada before tahajjud tomorrow, insha'Allah. I already know how to perform the farz prayers in general, and hope to start praying regularly from tomorrow with Allah’s help. I have a few questions and sorry if they seem basic: 1. Are the farz prayers and tahajjud prayer different? Do we say different duas in tahajjud compared to the regular obligatory prayers? 2. I'm still keeping this new faith private from my family and don't have a prayer mat. Can I pray on a clean bedsheet or any clean cloth instead? 3. I don't own a jilbab or special prayer clothes yet - is it okay to wear loose, full‑coverage clothing and a hijab for prayer? 4. I can't memorize many surahs or duas yet. Is it acceptable to read the dua or surah from my phone or a piece of paper while praying? 5. After finishing the rakats, must I remain seated in the exact posture used during tashahhud, or is it fine to fold my legs and then make duas and ask Allah for things? Sorry again if these are silly questions - I’m still learning and videos sometimes confuse me. I really want to try praying tahajjud on my first day, so please be kind and don't judge me 😊 JazakAllah khair.