Can I deduct a laptop both as a business startup cost and as asset being depreciated under business assets?

No, you cannot claim it twice.  Pick one option only. 

You cannot deduct a laptop both as a business startup cost and as a depreciable business asset; you must choose one method. If you include the laptop cost as part of your startup expenses, it is considered already claimed and amortized as a startup cost. In that case, you cannot also list it separately as a business asset to depreciate over time. Conversely, if you treat the laptop as a business asset, you capitalize it and depreciate it (or possibly expense it under Section 179 if eligible), but you cannot also include it in startup costs. Claiming it twice is not allowed.

Startup costs generally include expenses incurred to get your business up and running, and you can deduct up to $5,000 in startup costs in the first year if total startup costs are under $50,000, with the remainder amortized over 15 years. However, equipment purchases like laptops are typically capitalized and depreciated rather than deducted as startup costs.