Now that I think about them, they are very difficult question! In term of meaning, in very casual conversation, most of them are more or less the same. Sometimes they are interchangeable, sometimes (maybe) not. Putting them in sentences are very helpful; can't really think of their differences unless you give specific sentence. 1) Siapa-siapa and siapa saja; siapa-siapa saja = more or less the same. 'saja' gives emphasis. In this sentence though, 'Siapa saja yang ikut pesta kemarin?' emphasizes on who are the exact people. However, somehow if we replace siapa saja to siapa siapa, to me, it canNOT be a question. 'Siapa-siapa yang ikut pesta kemarin?' -- seems like no meaning, like we need something more for the sentence. 2) Semua and semuanya semuanya giving more emphasize, often are not interchangeable. Semua can be followed by Noun, semuanya cannot. 'Semua orang datang ke pesta kemarin.' ; CANNOT 'Semuanya orang datang ke pesta kemarin.' 'Semuanya datang ke pesta kemarin!' sounds like he is bragging! Emphasize that everyone came to the party yesterday. 3) tepat may be translated "exact", while sesuai "appropriate, fit". 4) untuk "for". agar "in order to". 'Alat ini untuk apa?' ; but NOT 'Alat ini agar apa?' 'Cuci tangan pakai sabun ini agar lebih bersih.' A gives result B. 5) Seberapa and beberapa are often used differently. While beberapa is often used in 'normal' sentences > countable items, seberapa sometimes put emphasize somewhere in the sentence and can also be used for uncountable items. 'Seberapa banyak indomie yang ia beli?' ; but NOT 'Beberapa banyak indomie yang ia beli?' 'Seberapa baik Ayah bekerja sepanjang hari untuk menghidupi kami sekeluarga.' ; but NOT 'Beberapa baik Ayah bekerja sepanjang hari untuk menghidupi kami sekeluarga.' 'Ayah membeli beberapa apel.' ; but NOT 'Ayah membeli seberapa apel.'

*moved to answer