how to recieve/cleanse mala bead for the first time

hi all, i am a born hindu as both my parents are hindu but i never fully understand the religion and had doubts as i was brought in tham anglo western part of australia. i am now taking time to read books/gita/and read articles online to help me understand the principles and philosophy of the Santana dharma. i would like to get a mala for mantras but i have some questions. 1. does it need to be 108 beads or is it ok to wear a smaller one and still count to 108 or a different number? 2 does a guru need to give it to u or can i just buy online? 3. how would i cleanse it as i have a dairy allergy and cannot soak it in ghee or fullfat mil/lactose free milk even if i clean it after (anaphylaxis) i drink soya milk. 4. must it be brown? i saw a green onr? i understand it is not a fashion statement but a representation of my worship to mata rani but i feel like i would connect with it more and be empowered with it if is i was able to choose? thank you!