No, you cannot mine from more than one device. Pioneers are only allowed one Pi account per person.
Pi uses a multi-pronged strategy to safeguard against fake accounts and bots. First, the network uses a combination of third party checks (e.g., recaptcha) and natively developed machine learning algorithms to identify bots. Such checks are usually invisible to most Pioneers.
Second, Security Circles, which are integral to the functioning of Pi’s consensus algorithm, also make it easy to detect fake accounts. Fake accounts will not have enough real people pointing at them via Security Circles. At best, fake accounts would be pointing at each other with very few incoming pointers from the rest of the network. This anomaly is easy to detect with computer algorithms.
Third, Pi’s native, decentralized KYC solution helps validate the identity of Pioneers before they are eligible to migrate their mined mobile Pi balance onto the Mainnet blockchain. In other words, only accounts validated as belonging to distinct real individuals will be honored on the Mainnet blockchain. KYC also acts as a final system check against bots and fake accounts. That is, even if all other methods missed out on some “bot” accounts, this Pioneer validation process will further eliminate them because bot owners will not be able to prove bots to be real people with real names and government-issued identity cards.